[simprod-scripts] always use the GPU over the CPU with PPC

[David Schultz]

The ordering between GPU and CPU using opencl is random. Make it fixed, with the GPU always first.

In fact, maybe just only use the GPU unless told otherwise? Or at least have some configuration for this.

[Nakul Aggarwal]

My guess is the ordering depends on the version of the driver or which card is used? More information would be welcome. PPC will use the driver-provided list of devices in the order that the driver provides it in.

The requested option already exists: you can set env. variable OGPU=1 to only use GPUs, OCPU=1 to only use CPUs, or OACC=1 to only use accelerator cards. You can also combine these, though that is not recommended as the fastest device will be underused (unless more tweaking is done to settings such as number of photons per thread for each device are specified separately).

[David Schultz]

The driver version was the same (it was the same machine).

Since the option exists, I change my request to actually using the option.

[Juan Carlos Díaz Vélez]

Rev. 141251 commit. Sets OGPU=1 by default unless CPUs are requested.

[Alex Olivas]

Milestone IceSim? 5.0 deleted